1. Industrial Field of the Invention
The present invention relates to a discharge element to be used in charging or discharging fine particles, charging or discharging photoelectrically conductive insulation film used in electronic copying machines, surface treatments of plastics, and generation of ozone from oxidants The present invention further relates to a discharge apparatus having a structure that combines such a discharge element with the power source for the same, and also relates to a discharge treatment apparatus having a structure that combines the above-described discharge apparatus with an auxiliary electrode, a power source and a device for handling a subject
2. Description of the Related Art
A conventional element for use in the above-described types of applications comprises an electrically conductive strip electrode mainly comprising a metal provided on the surface of a ceramic insulating body with a planar electrode provided on the inside of the former. Therefore, when a high frequency, silent creeping discharge is generated on the surface of such a ceramic insulating body during the application of high frequency voltage, the strip electrode is partially consumed and is thus deformed to take an irregular shape, or a part of the body thereof may be melted and splashed over the surface of the ceramic insulation body, causing the electrical field to be disordered. This causes its efficiency as an ion source to deteriorate. These phenomena can also result from oxidation of the surface of the electrode and the thus-generated oxide exhibits a low melting point. These phenomena can also occur because the oxidation products are chemically unstable.
A so-called grading method is known as a method to prevent the above-described problems, wherein both the surface of the liner electrode and the same of the ceramic insulating body are sealed with a molten glass coat. However, if the thickness of the coat is too thin, the glass coating is subject to premature breakdown. On the other hand, if the glass coating is too thick, the insulating characteristics of the grading layer prevent the generation of sufficient ions, thus requiring the application of a rather high voltage in comparison to the case where no grading is performed. In addition, the melting point of the grading layer is not sufficiently high to prevent generation of fine particles from the grading layer when discharge is performed. Therefore, when such discharge element is used in gas treatment, the treatment gas generated is contaminated by the above-described fine particles, causing the quality of the subject to be critically affected. In particular, when ozone is generated using ferment as a material by a conventional discharge element for the purpose of using it to manufacture semiconductor products, boron, which is contained in a grading material applied on alumina generally used as a ceramic insulating material of a discharge element, contaminates gas containing generated ozone. The thus-contaminated ozone can critically affect the quality of the semiconductor products.
In addition, a known method is employed in which fine ceramics represented by 92% or more alumina is used as the insulating material, and in order to form an electrically conductive strip electrode on the surface of the fine ceramics in an integrated manner with it and to form a planar electrode on the inside of the same also in an integrated manner, the two electrodes are printed by a thick-film technique in a green sheet process. Then, they are press-welded to each other before being baked in a hydrogen atmosphere for a certain long time period so as to be metalized for the purpose of manufacturing a thick-film multilayered printed ceramic substrate. In the thus-manufactured discharge element, the thermal expansion coefficient of the alumina fine ceramics which serves as the insulating material and that of the material for the electrodes are made approximately the same in a significantly wide temperature region from room temperature to approximately 1500 degrees C. Therefore, materials other than paste mainly made of tungsten cannot be used as the material for the electrodes. However, since tungsten displays relatively poor resistance against oxidation at high temperatures, a problem arises in that the electrodes are consumed by oxygen usually contained in an atmosphere for cases where the discharge element is used. As a result of this, performance cannot be stably maintained through a long time period. Furthermore, in the known method of manufacturing discharge elements for the above-described thick-film multilayered printed ceramic substrates, semiconductor ceramics are used as the material for electrodes. However, if the material for the electrodes is replaced by a semiconductor, heating occurs at the electrode or the voltage of the electrode resistor drops since semiconductors literally offer a great electrical resistance. As a result of this, the voltage which is applied to the electrode disposed away from the power supplying portion is reduced, causing the efficiency to deteriorate. Consequently, an electrical field apparatus which can be put into practical use cannot be obtained. Furthermore, the above-described manufacturing methods suffer from the critical disadvantages that they need expensive manufacturing facilities, and require a lengthy processing to complete the products. Therefore, the manufacturing costs with the above-described methods become great.
An object of the present invention is to overcome the above-described problems experienced with the conventional discharge elements. That is, an object of the present invention is to prevent occurrence of phenomena that a linear electrode is consumed and is thus deformed to take an irregular shape, or the same splashes and adheres to the surface of the ceramic insulating material.
Another object of the present invention is to avoid a necessity of raising the voltage to be applied even if a film is formed on the surface of such linear electrode so as to improve the durability of it.
A further object of the present invention is to reduce the manufacturing cost by simplifying the manufacturing method for the discharge element, and to make the types of the materials capable of being used various in accordance with the object of use for the purpose of widening the application scope for the discharge element.